This invention relates generally to apparatus for measuring the volumetric and mass flow of gases and liquids, and more particularly to a vortex flowmeter system capable of metering fluids of different densities and of providing correct readings for each fluid.
Petroleum found in rock formations is recovered therefrom by drilling a well. After completion, a well may flow freely, producing thousands of barrels a day as a result of high "reservoir" pressure generated by natural gas trapped with the oil, or by the pressure of water layers above the oil. In order to increase oil recovery, it is common practice to pump water or gas down one well to increase the flow from adjacent wells in the same rock formation.
Thus, emerging from the oil well is not merely oil, for the output may take the form of a stream of oil interspersed with gas, the alternate flow of gas and oil being random in nature. Or the oil output of the well may be intermingled with water.
It is desirable in an oil recovery installation to measure the output of the wells so that one can maintain proper productivity records. While vortex-type flowmeters are capable of measuring volumetric flow and mass flow, they are incapable of discriminating between gas and liquid, and their readings are therefore not a true indication of how much oil has been produced, as distinguished from water and gas also yielded by the producing well.
My prior U.S. Pat. No. 3,776,033 discloses a vortex-type flowmeter which is useful in many industrial processes and gas supply systems, the meter being capable of measuring the mass flow as well as the volumetric flow of fluids being treated or supplied. A meter of this type is operative in those situations in which the fluid being metered is either entirely in liquid or in gas form, for then the meter would indicate the volumetric flow of the fluid and its mass flow. The same meter can also be made to indicate the density of the fluid being metered.
But where the fluid flowing through a meter of this type is intermittently in liquid and gaseous form or is a mixture of liquids of different density, the meter is incapable of providing indications that distinguish between liquid and gas or between liquids of different density. Hence such meters are not useable in oil recovery installations or in other situations in which the fluid stream is of variable density.